One of the most important traits investors must have is patience -- the patience to hold shares of great companies through good times and bad times, and even in the face of major market volatility. For investors disciplined enough to pull this off, the magic of compounding will do the rest. But this strategy works if, and only if, the stocks you select are indeed those of winning companies.

With hundreds of options to choose from on the market, it can be hard to separate the wheat from the chaff. Today, let's look at two companies that look well on their way to remain leaders in their respective industries for years to come. The companies in question are pharma giant Johnson & Johnson (JNJ -0.42%) and fintech specialist Square (SQ 0.89%). Let's see why both are worth adding to your portfolio.

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1. Johnson & Johnson

Johnson & Johnson has been grabbing scores of headlines lately thanks to its effort to develop a vaccine for COVID-19. This opportunity may provide a nice boost to the drugmaker in the short term, but in the long run, the pharma giant will benefit even more from the world's need for innovative drugs. This factor will be all the more important given our aging population.

Johnson & Johnson's pharmaceutical business is its most lucrative. During its fiscal 2020, sales from this segment were $45.6 billion, an 8% year-over-year increase that accounted for about 55% of the company's total revenue. Johnson & Johnson boasts more than half a dozen blockbuster products, which are drugs with annual sales exceeding $1 billion. Most pharma companies would consider themselves lucky to have just one.

For instance, there is plaque psoriasis treatment Stelara, for which fiscal 2020 revenue was up 21% to $7.7 billion. There is also cancer treatment Darzalex, which brought in sales of $4.2 billion in 2020, a 39.8% increase compared to the previous fiscal year. Imbruvica, another cancer treatment, recorded $4.1 billion in sales in 2020, 21% higher than in 2019.

These drugs (and others) are helping the pharma giant recoup some of the losses it is incurring elsewhere. For instance, sales of rheumatoid arthritis treatment Remicade dropped by 14.4% in 2020 to $3.7 billion. The decline was due to competition from biosimilars. But note that Johnson & Johnson has well over two dozen ongoing late-stage clinical trials, and an even greater number of phase 1 or phase 2 studies.

These candidates give the drugmaker plenty of opportunities to make up for products whose sales are stalling. The company had more than half a dozen approvals or regulatory submissions in the fourth quarter alone. Johnson & Johnson's pharmaceutical segment is well-positioned to keep adding new products to its lineup (or add new indications to existing products) practically every quarter.

One big concern with Johnson & Johnson are the lawsuits that plague the company. However, I am not, as a shareholder, worried about these potential legal issues. The company recognizes financial losses from these ongoing lawsuits in its financial statements when these losses can be "reasonably estimated." 

And having dealt with thousands of such lawsuits over the past few decades, the company does not think its current legal problems will have any material effect on its financial position.  For instance, during the fiscal year 2020, the drugmaker spent $5.1 billion in litigation expenses (the same amount as it spent in 2019), which amounted to just 6.1% of its sales for the year.

This potential headwind aside, the strength of Johnson & Johnson's pharmaceutical business, coupled with its medical devices and consumer healthcare segments, makes this pharma stock worth stashing in your portfolio for decades to come.

2. Square

"We believe everyone should be able to participate in the economy," says financial services specialist Square, front and center on its website. How is the company doing its part to make this goal a reality? First, Square appeals to small and medium-sized business owners by offering efficient options for payment processing. The company also offers payroll services, small business loans, e-commerce services, invoices, and more.

Square's library of products is vast, and although many of its competitors offer alternatives to some of its solutions, few offer as many in one spot. Once a business joins Square's ecosystem, it is likely to expand the range of solutions it purchases from the financial services company. CEO Jack Dorsey once referred to Square's ecosystem as being "extremely sticky," which gives it a powerful competitive advantage.

Square has also branched out in the personal financial services area thanks to its peer-to-peer mobile payment app, Cash App. The app now allows users to invest in stocks or cryptocurrencies, as well. Cash App also offers direct deposits and a debit card with ATM withdrawal options. Square's Cash App and its seller ecosystem continue to help it deliver strong financial results. 

Point of sales system at store counter

Image source: Getty Images.

During its fourth-quarter 2020 ending Dec. 31, the company reported total net revenue of $3.2 billion, representing a 140.5% year-over-year increase. Square's gross profit for the quarter grew by 52% year over year to $804 million. Meanwhile, Cash App gross profit was $377 million, 162% higher than the year-ago period. Square's seller ecosystem recorded a gross profit of $427 million, 13% higher than the prior-year quarter.

Square still has a long runway for growth, making it an excellent stock to stash in your portfolio for decades to come. Analysts see the company's top line increasing by 39.6% throughout the next five years. Square has tapped into less than 3% of a $100 billion opportunity for its seller ecosystem and less than 2% of a $60 billion opportunity for its personal financial services offerings.

Thanks to the "stickiness" of its seller ecosystem and increased brand recognition, the company looks set to continue cashing in on these long-term opportunities for many years to come. Because of these factors, there is little doubt in my mind that in 10 years -- or even looking at a longer time span -- Square's stock will have more than doubled.